"I have not observed the situation of the occipital opening of the jacko or orang-outang (_Simia satyrus_ L.); but as I know that this animal almost habitually walks erect, though it has no strength in its legs, I suppose that the occipital foramen is not situated so far from the base of the skull as in the other _Quadrumana_. "The head of the negro, less flattened in front than that of the European man, necessarily has the occipital foramen central. "The more should the jacko contract the habit of walking about, the less mobility would he have in his toes, so that the thumbs of the feet, which are already much shorter than the other digits, would gradually cease to be placed in opposition to the other toes, and to be useful in grasping. The muscles of its lower extremities would acquire proportionally greater thickness and strength. Then the increased or more frequent exercise of the fingers of its hands would develop nervous masses at their extremities, thus rendering the sense of touch more delicate. This is what our train of reasoning indicates from the consideration of a multitude of facts and observations which support it."[196] The subject is closed by a quotation from Grandpré on the habits of the chimpanzee. It is not of sufficient importance to be here reproduced. Seven years after the publication of these views, Lamarck again returns to the subject in his _Philosophie zoologique_, which we translate. "_Some Observations Relative to Man_. "If man were distinguished from the animals by his structure alone, it would be easy to show that the structural characters which place him, with his varieties, in a family by himself, are all the product of former changes in his actions, and in the habits which he has adopted and which have become special to the individuals of his species. "Indeed, if any race whatever of _Quadrumana_, especially the most perfect, should lose, by the necessity of circumstances or from any other cause, the habit of climbing trees, and of seizing the branches with the feet, as with the hands, to cling to them; and if the individuals of this race, during a series of generations, should be obliged to use their feet only in walking, and should cease to use their hands as feet, there is no doubt, from the observations made in the preceding chapter, that these _Quadrumana_ would be finally transformed into _Bimana_, and that the thumbs of their feet would cease to be shorter than the fingers, their feet only being of use for walking.